PostgreSQL provides a large
number of functions and operators for the built-in data types.
Users can also define their own functions and operators, as
described in Part V. The
psql commands \df and \do can be used
to list all available functions and operators, respectively.

If you are concerned about portability then note that most of
the functions and operators described in this chapter, with the
exception of the most trivial arithmetic and comparison operators
and some explicitly marked functions, are not specified by the
SQL standard. Some of this
extended functionality is present in other SQL database management systems, and in many
cases this functionality is compatible and consistent between the
various implementations. This chapter is also not exhaustive;
additional functions appear in relevant sections of the
manual.